The present invention is broadly directed to shock absorbers for use with wheeled vehicles to cushion against impacts during use. The present invention is more particularly directed to shock absorbers disposed in the seated region of a wheeled vehicle, such as a bicycle and the like, to cushion the seat assembly and the drive assembly relative to impacts occurring during operation by imparting common movement thereto. A cycle incorporating such a shock absorber and a methodology for cushioning impact during operation of a cycle are also provided.
While the origin of the bicycle dates as far back as the mid-17th century, when wheeled vehicles were moved by the action of pushing on the ground with one""s feet, the real technical innovation in this domain came in the early 19th century with the invention of swinging pedal cranks for two wheeled vehicles. At that time, swinging pedal cranks were placed on either side of the front wheel of the bicycle which transmitted a movement to the rear wheel by means of two light connecting rods. This invention was not very successful because the pedals did not rotate, but rather followed circular arcs which caused rider fatigue in the knee joints. The invention which really advanced the innovation of the bicycle came in the mid 1800s when pedal cranks were made to pivot integrally around the axle of the front wheel, to which the pedals transmitted their movement directly. This invention was known as the velocipede. Later that century, spoked wheels and metal frames were designed which made the vehicle appreciably lighter, as well as the incorporation of an endless drive chain to transmit energy directly to the rear wheel.
Bicycles have long been used as a means for both transportation and recreation. In fact, in some countries throughout the world the bicycle is the primary mode of transportation, replacing automobiles, trains, buses, etc. Prior art bicycles abound with design variations concerning primarily size, weight, appearance, flexibility and reliability. There are various types and configurations of bicycles available, the two most popular of which are the mountainbike and the twenty-one speed, or racing, bike. Regardless of its type, the conventional bicycle is generally characterized by a frame which rotatably supports a plurality of wheels, a steering mechanism mounted to the frame for controlling movement of the wheels, a drive assembly interconnected between the frame and the wheels for imparting rotary movement to the wheels, and a seat upon which the user is supported for transport.
Recent innovations in the evolution of the bicycle have involved improving its shock absorption characteristics. This is particularly true for mountain- bikes which are especially designed to be ridden over rugged terrain. Due to their relatively rigid frames, bicycles transmit shocks resulting from bumps, pot holes, rocks or other discontinuities in the riding surface directly to the rider. Such surface discontinuities, over prolonged period of riding time, can result in discomfort to the rider and increased fatigue as the rider attempts to reposition himself/herself on the bicycle in anticipation of upcoming obstacles.
In an effort to provide a more comfortable environment for the rider, manufacturers have designed various types of shock absorption systems for use primarily with the front and rear wheels of the bicycle. Much like the suspension systems associated with automobiles, bicycle shock absorbers allow the rider to travel smoothly over the rugged terrain. While the bicycle""s wheels may jolt up and down, springs between the wheels and the bicycle frame flex and absorb the force of these jolts. This ensures that the force of the bumping is not transferred to the rider. Springs alone tend to produce a bouncing motion, so the suspension system may also incorporate dampers, which slow the movement of the springs to prevent the bicycle and its rider from bouncing up and down.
It is also known to incorporate shock absorbers in other areas of the bicycle frame. For example, U.S. Pat. No. 5,217,241, issued Jun. 8, 1993, relates to such a suspension system which is capable of transforming pedal force into forward motive force when in high gears, while providing increased traction in the lower gears. Here, the shock absorber system comprises a pair of tubular chain stays disposed on either side of the bicycle""s rear wheel, first ends of which pivot relative to the frame""s seat tube, and second ends of which are joined to a seat stay. Disposed on the seat stay is a displacable spring assembly secured to the upper portion of the seat tube. As the bicycle frame experiences a load while the rear wheel remains affixed against the ground, the chain stays are urged to rotate upwardly about their pivot point. The load force and resulting displacement are transferred directly from the rear axle through the seat stays to the spring assembly.
While the forgoing bicycle shock absorption systems are useful in their own right, there remains a need to provide a new and improved shock absorber for bicycles, or other types of cycles, for cushioning impact in the seated region. It would be desirable for such a shock absorber to be adjustable so that absorption characteristics can be selectively varied with little difficulty by the rider. It would further be desirable for such a shock absorber to be substantially concealed from view within the frame of the cycle so that the cycle is both aesthetically pleasing, yet still able to accommodate various accessories frequently mounted to the bicycle frame. The present invention is directed to meeting these needs, among others.
It is an object of the present invention to provide a new and improved shock absorber for use with wheeled vehicles, such as bicycles, tricycles, motorcycles and the like, to cushion against impacts occurring during operation.
Another object of the present invention is to provide a new and improved shock absorber for use with a cycle, which shock absorber is a substantially concealed from view so that it resembles other conventional cycles.
A further object of the present invention is to provide a new and improved shock absorber for cycles which is adjustable by a rider to selectively vary shock absorption characteristics.
Still a further object of the present invention to provide such a shock absorber which is relatively lightweight so that it has minimal effect on the overall weight of the cycle.
Yet another object of the present invention is to provide a new and improved method for cushioning impact during operation of a cycle.
In accordance with these objectives the present invention relates to a shock absorber for use with a cycle adapted to travel in an upright position along a support surface to cushion against impacts. Here, the cycle includes a rigid frame adapted to rotatably support a plurality of wheels, a drive assembly including a pair of foot supports operative upon actuation to impart rotary movement to one of the wheels, and a seat assembly.
The shock absorber broadly includes first and second elongated tubular members and a biasing assembly coupled therebetween. The first elongated tubular member is associated with the frame and the second elongated tubular member has a lower end portion adapted for connection to the drive assembly""s foot supports and an opposite upper end portion adapted for connection to the seat assembly such that the foot supports and the seat assembly are interconnected for common movement. The second tubular member is slidably disposed with respect to the first tubular member for movement along the first tubular member""s longitudinal axis away from an initial position as determined by a pre-impact condition.
The biasing assembly is coupled between the first and second tubular members so that movement of the second tubular member in a first direction along the longitudinal axis away from the initial position is resisted by the biasing assembly. The biasing assembly is further operative in response to such movement in the first direction to exert a restorative force to urge the second tubular member in a second direction along a longitudinal axis of the first tubular member and toward the initial position, thereby to cushion the seat assembly and the drive assembly relative to impacts occurring during operation of the cycle.
To this end, the biasing assembly includes a first biasing seat disposed for common movement with the first tubular member and a second biasing seat disposed for common movement with the second tubular member. The biasing seats may be disposed either within an interior of the second tubular member or exteriorly thereof. Where the first and second biasing seats are disposed exteriorly of the second tubular member, they may be in the form of brackets mounted, respectively, to the first and second tubular members. A resilient member is interposed for compression and expansion between the first and second biasing seats. This resilient member may be a spring, a compressible polymer, a spring/polymer composite, or the like.
Preferably, the second tubular member is telescopically received within the first tubular member and has its sidewall provided with a pair of diametrically opposed tracking slots. Preferably also, the sidewall of the first tubular member is provided with a pair of diametrically opposed apertures that are alignable with the tracking slots of the second tubular member, and a guide pin extends through the tracking slots and the apertures. Particularly, the guide pin extends through the first biasing seat to fixedly mount the first biasing seat within the interior of the first tubular member.
The biasing assembly may also include a pre-load mechanism operative upon actuation to selectably adjust the restorative force of the biasing assembly when in the pre-impact condition. The pre-load mechanism may include a plunger having a plunger shaft adjustably mounted to the second biasing seat and a plunger head in contact with the resilient member. Preferably, the plunger shaft is threadedly mounted to the upper biasing seat whereby rotation of the plunger shaft relative to the upper biasing seat operates to adjustably vary the restorative force of the resilient member.
The present invention also contemplates a method for cushioning impact during operation of a cycle which is adapted to travel in an upright position along a support surface. This methodology broadly comprises a first of rigidly interconnecting the cycle""s seat assembly and the drive assembly""s foot supports for reciprocal, common movement in upward and downward directions relative to the frame. The methodology also includes a second step of exerting a restorative force on the seat assembly and the foot supports to urge them upwardly toward an initial position relative to the frame in response to a displacement of the seat assembly and foot supports in a downward direction away from this initial position.
These and other objects of the present invention will become more readily appreciated and understood from a consideration of the following detailed description of the exemplary embodiments when taken together with the accompanying drawings, in which: